I have a 6 1/2 inch ruler that I love. I dont know if you can tell from the pic, but at one corner it starts out with whole inches with the extra half on the end. From the oppisite corner it marks the half inch at the beginning. Plus you can flip it to either have black or yellow lines.
http://us.st12.yimg.com/us.st.yimg.c...021_1267575120
As for duds....I'd say my fabric pens/pencils/chalk/whatever. I can't seem to find one I like.